The Relations Between Pedagogical and Scientific Explanations of Algorithms: Case Studies from the French Administration

The opacity of some recent Machine Learning (ML) techniques have raised fundamental questions on their explainability, and created a whole domain dedicated to Explainable Artificial Intelligence (XAI). However, most of the literature has been dedicated to explainability as a scientific problem dealt with typical methods of computer science, from statistics to UX. In this paper, we focus on explainability as a pedagogical problem emerging from the interaction between lay users and complex technological systems. We defend an empirical methodology based on field work, which should go beyond the in-vitro analysis of UX to examine in-vivo problems emerging in the field. Our methodology is also comparative, as it chooses to steer away from the almost exclusive focus on ML to compare its challenges with those faced by more vintage algorithms. Finally, it is also philosophical, as we defend the relevance of the philosophical literature to define the epistemic desiderata of a good explanation. This study was conducted in collaboration with Etalab, a Task Force of the French Prime Minister in charge of Open Data & Open Government Policies, dealing in particular with the enforcement of the right to an explanation. In order to illustrate and refine our methodology before going up to scale, we conduct a preliminary work of case studies on the main different types of algorithms used by the French administration: computation, matching algorithms and ML. We study the merits and drawbacks of a recent approach to explanation, which we baptize input-output black box reasoning or BBR for short. We begin by presenting a conceptual framework including the distinctions necessary to a study of pedagogical explainability. We proceed to algorithmic case studies, and draw model-specific and model-agnostic lessons and conjectures

Rheological performance evaluation of asphalt modified with bio-based polymers

Fuel-based polymers, used as modifiers and additives in asphalt cement binders, improve the rheological performance of the base asphalt binders, therefore increase the resistance to pavement distresses. However, demand for polymers that are biodegradable, environmentally friendly, and cost effective is increasing. Soybean oil used as an alternative in place of soft and rubbery elastomers polybutadiene derived from crude oil was synthesized to bio-based polymers via chemical synthesis methods reversible addition-fragmentation chain transfer (RAFT) and atom transfer radical polymerization (ATRP). In this study, bio-based polymers (PS-PAESO and PS-PAESO-Cl) with different styrene parameters were blended at a dosage of 3% by weight to a base asphalt binder by the solvent blending approach and three different shear blending methods. The objective of this study was to characterize the rheological properties of bio-based polymer modified asphalt blends by conducting dynamic shear rheometer (DSR), rolling thin film oven (RTFO), pressurized aging vessel (PAV), and bending beam rheometer (BBR) based on the Superpave performance graded asphalt binder specifications. The complex modulus (G*), phase angle (δ), mass losses, creep stiffness were determined to evaluate the rheological properties of the modified blends. Statistical analysis was conducted to evaluate the related factors that may influence the test results and to develop statistical modeling for predicting the bio-based polymers with appropriate styrene parameters that would optimize the rheological performance of the modified blends. Results from high temperature performance tests show that the addition of bio-based polymer (PS-PAESO and PS-PAESO-PS) used in this study increase the critical high temperature of the base binder that indicate an improvement on the resistance of rutting at high temperature. The similar results are observed from the master curves and the black diagrams which both exhibit stiffer behavior of the base asphalt at higher temperatures after modification, which indicates a rubber-elastic network establishment within the blends. Whereas, these bio-based polymers do not substantially improve the resistance to low temperature thermal cracking based on the critical low temperature results. Another finding is the use of bio-based polymers generally widened the continuous performance grade range of the base asphalt binder, which indicates that the bio-based polymers reduce the temperature susceptibility of the base asphalt binder. Furthermore, the statistical analysis on laboratory test results show no statistically significant difference between the three shear blending methods used in this study and no statistically significant difference between the polymer synthesis reaction durations. However, further statistical analysis by using block design on the shear blending methods and the polymer reaction durations shows there is statistically significant difference between the short and long reaction durations but no statistically significant difference between the shear blending methods. The finalized prediction models based on the response surface modeling present the same predicated styrene parameters in polymer to the test result analysis, which indicates that bio-based polymer with styrene parameters as lower molecular weight and lower styrene content are recommended for achieving higher critical high temperatures

Can we exploit machine learning to predict congestion over mmWave 5G channels?

It is well known that transport protocol performance is severely hindered by wireless channel impairments. We study the applicability of Machine Learning (ML) techniques to predict congestion status of 5G access networks, in particular mmWave links. We use realistic traces, using the 3GPP channel models, without being affected using legacy congestion-control solutions. We start by identifying the metrics that might be exploited from the transport layer to learn the congestion state: delay and inter-arrival time. We formally study their correlation with the perceived congestion, which we ascertain based on buffer length variation. Then, we conduct an extensive analysis of various unsupervised and supervised solutions, which are used as a benchmark. The results yield that unsupervised ML solutions can detect a large percentage of congestion situations and they could thus bring interesting possibilities when designing congestion-control solutions for next-generation transport protocols.This work was supported by the Spanish Government (MINECO) by means of the project FIERCE “Future Internet Enabled Resilient smart CitiEs” under Grant Agreement No. RTI2018-093475-A-I00

Targeting TMEM16A to reverse vasoconstriction and remodelling in idiopathic PAH

Our systematic analysis of anion channels and transporters in idiopathic pulmonary arterial hypertension (IPAH) showed marked upregulation of the Cl- channel TMEM16A gene.We hypothesised that TMEM16A overexpression might represent a novel vicious circle in the molecular pathways causing PAH.We investigated healthy donor lungs (n=40) and recipient lungs with IPAH (n=38) for the expression of anion channel and transporter genes in small pulmonary arteries and pulmonary arterial smooth muscle cells (PASMC). In IPAH, TMEM16A was strongly upregulated and patch-clamp recordings confirmed an increased Cl- current in PASMC (n=9-10). These cells were depolarised and could be repolarized by TMEM16A inhibitors or knock-down experiments (n=6-10). Inhibition/knock-down of TMEM16A reduced proliferation of IPAH-PASMC (n=6). Conversely, overexpression of TMEM16A in healthy donor PASMC produced an IPAH-like phenotype. Chronic application of benzbromarone in two independent animal models significantly decreased right ventricular pressure and reversed remodelling of established PH.Our findings suggest that increased TMEM16A expression and activity comprise an important pathologic mechanism underlying vasoconstriction and remodelling of pulmonary arteries in PAH. Inhibition of TMEM16A represents a novel therapeutic approach to achieve reverse remodelling in PAH

Cellular and biochemical effects induced by antiretroviral drugs.

Ph. D. University of KwaZulu-Natal, Durban 2013.In the treatment of HIV/AIDS, protease inhibitors (PIs) and nucleoside/nucleotide analogue reverse transcriptase inhibitors (NRTIs) are the major components of highly active antiretroviral therapy (HAART). The side effects of these drugs include various metabolic disorders including insulin resistance, dyslipidaemia and lipodystrophy. The precise mechanistic basis of these remains largely unknown. In this study we aimed to understand the molecular basis of these metabolic effects by analysing the effects on lipoprotein lipase (LPL) activity, insulin signaling and the cellular metabolic profile. It was previously shown by this group that indinavir inhibits insulin signaling at a proximal level. The study was extended to a wider range of ARVs and in particular, the effects of sodium salicylate (NaSal) and berberine chloride (BBR) were analysed to determine if they could reverse the effects of the drugs on insulin signalling. In addition, Chinese hamster ovary cells transfected with the human insulin receptor (CHO-IR) were used for the first time to study the effects of NRTIs on the insulin signaling pathways. The high level of expression of insulin receptor facilitated sensitive detection of any alteration in the phosphorylation of signaling proteins as compared to 3T3-L1 adipocytes. Three PIs, indinavir, nelfinavir and ritonavir were used in this study. Indinavir and nelfinavir treatment significantly reduced the insulin-stimulated phosphorylation of the IRβ, IRS-1, Akt and MAPK in CHO-IR cells. However phosphorylation of GSK-3α\β was not affected by the PIs. Ritonavir also decreased (not statistically significant) the phosphorylation of IR-β and IRS-1 but its inhibitory effect on MAPK was the same as by the other PIs. NRTI’s did not inhibit insulin-stimulated tyrosine phosphorylation of IRβ and IRS-1 but reduced phosphorylation at MAPK and Akt. In order to understand the role of NFκ-B pathway in blocking insulin-stimulated tyrosine phosphorylation, IKK-16, a selective inhibitor of IkB kinase (IKK) was used but no significant involvement of this pathway was found in blocking tyrosine phosphorylation at IRS-1. Similarly, NaSal and BBR were also used to reverse the effects induced by PIs and NRTIs in CHO-IR cells but no significant change was observed on Akt and MAPK. NaSal and BBR reduced (but not significantly) the effects of PIs (indinavir and nelfinavir) on IR-β and IRS-1. These findings suggest that PIs induce insulin resistance by affecting multiple steps in the signaling pathway. At the proximal end of the insulin signalling pathway, protease inhibitors affect IR-β and IRS-1 while at the distal end they affect phosphorylation of Akt and MAPK. CHO-IR cells were also used to measure LPL activity using a colorimetric method employing pNPB as substrate. The most commonly used ARVs were tested. These included four PIs and six NRTIs .The results showed that NRTIs stavudine and emtricitabine significantly inhibited the LPL activity from the CHO-IR cells. PIs indinavir and nelfinavir were also found to decrease LPL activity extracellularly when added to the assay reaction in vitro. Similarly nelfinavir and atazanavir sulfate inhibited the activity of the LPL from the CHO-IR cells after 16 hour treatment. This suggested that these drugs may interfere with the enzyme activity intracellularly either at the level of its synthesis or its transportation from cytoplasm to the cell surface. These finding suggests that protease inhibitors may play a role in inhibiting lipoprotein lipase activity in vivo, and may thereby induce metabolic disorders in HIV-positive patients being treated with protease inhibitors. Metabolomic analysis was performed on the supernatant of cells treated with PIs and NRTIs, with and without insulin stimulation. Many significant alterations and trends in amino acids and organic acids levels in CHO-IR cells supernatants (treated with PIs) were recorded using 1H-NMR. For example, PIs decreased the synthesis of threonine, phenylalanine, lysine, arginine, isoleucine butyrate, glutamate, histidine and 2-oxo-isovalerate. Furthermore overproduction of lactate and ketones were observed in the nelfinavir treated cells. This may be a consequence of the secondary effects of insulin resistance induced by the PIs. Similarly NRTIs (stavudine and tenofovir) treatment also induced changes in the levels of many amino acids and organic acids .NRTIs decreased the synthesis of acetate, acetoacetate, histidine, methionine, phenylalanine and tryptophan while significant increase in the acetone was observed in stavudine-treated cells. Taken together, the results of this study suggest that PIs and NRTIs, inhibits LPL activity and synthesis, affects insulin signalling pathways at different levels and alters the synthesis of different cellular metabolites which may affect the signalling pathways of insulin

PeatFire: an agent-based model to simulate fire ignition and spreading in a tropical peatland ecosystem

The increased frequency and spread of tropical peat fires over the last two decades have attracted global attention because they cause significant environmental and health impacts at local to global scales. To understand the relative importance of key factors controlling tropical peatland burning events, we developed PeatFire, an agent-based model simulating the interaction between human-induced ignitions, fire and peat characteristics. The model describes (1) above- and belowground fires, which spread independently but interact with each other; (2) above- and belowground biomass; and (3) the watertable determining peat dryness and susceptibility to fire. We applied PeatFire to a region in South Sumatra that has experienced profound natural rainforest loss due to peat fires. Sensitivity analysis of the model suggests that fire sizes depend mostly on watertable depth, peat-dry-index and number of dry days before ignition. Using pattern-oriented modelling, these factors were parameterised so that the model output matches spatiotemporal fire patterns observed in the study region in 2015. Our results emphasise the risk of a sudden shift from moderate fire occurrence to complete burning and highlight the importance of local context to peatland regulation, which should consider both biophysical and socioeconomic factors and strategies for peatland fire management

Pathogenesis of Bartonella Henselae in the Domestic Cat: Use of a PCR-based Assay for the Detection and Differentiation of B. Henselae Genotype I and Genotype II in Chronically Infected Cats.

Bartonella henselae is a zoonotic agent in which the domestic cat serves as the natural reservoir, and humans acquire potentially serious infections associated with this microorganism. The purpose of this research is to contribute to the understanding of the pathogenesis of B. henselae in the domestic cat using a molecular approach. Using sequence differences in a portion of the I 6S rRNA gene between B. henselae genotype I, and B. henselae genotype II, a nested polymerase chain reaction (nPCR) was designed and used to investigate various phases of feline bartonellosis. The nPCR detected 3.2 organisms per milliliter of blood which is below the detection limits of standard bacterial culture. Bartonella henselae LSU 16 genotype II, Bartonella henselae Baby genotype II, Bartonella henselae 87--66 genotype I, and Bartonella henselae Houston-1 genotype I were used in this study to infect cats. The PCR assay detected Bartonella DNA in 40 blood samples that were culture negative. The bacteremia as determined by PCR lasted for a period of 1 to 9 weeks longer than determined by culture methods in 10 of the 16 cats. An episode of relapsing bacteremia occurred in two cats during the infection. Of the twenty-three cats examined, Bartonella DNA was detected in various tissues from 10 of the 23 cats. The spleen of nine of the 10 cats was positive for Bartonella DNA. The other tissues in which Bartonella DNA was detected included bone marrow, lymph node, kidney, lung, liver, brain, and heart valve. Histopathological lesions associated with nonspecific antigenic stimulation were seen in the cats but organisms could not be visualized in tissue. RNA expression analysis using the RT-PCR assay with primers specific for the 16S rRNA and the citrate synthase gene (gltA) of Bartonella detected no Bartonella RNA expression in the tissue of infected cats. Bartonella genotypes remained the same throughout the period of the acute bacteremia and in the recurring bacteremia as determined by the PCR assay. The persistent Bartonella DNA detected in tissue was B. henselae genotype II. B. henselae genotype I was not detected in any of the infected cats

Metropolitan regions and spatial development: part 4, Metropolitan regions as a new spatial planning concept - aspects of implementation, using the example of South-Western Germany

Implementation of the metropolitan region concept in planning practice was the topic of a recent research project carried out at the university of Tübingen. Key questions include how this policy, aimed at enhancing the competitiveness of metropolitan regions, is implemented, what opportunities it offers and what obstacles and challenges have to be overcome. The extensive empirical investigation presented here focuses on the actual implementation process in Baden-Württemberg, which presents a multi-faceted implementation landscape with a variety of different approaches, including the oldest and youngest generation of accredited metropolitan regions as well as cross-border areas of infl uence. The analysis of surveys of community offi cials combined with extensive interviews with stakeholders and planning authorities provides insight into a dynamic process and highlights signifi cant differences in planning and implementation practices. A considerable gap is revealed between planning theory and practice, especially in terms of fl exible geometries and metropolitan governance structures. The increasing discrepancy between functional and administrative territories has led to over-extension trends as well as to fears of marginalisation. The envisaged concept of large scale communities of responsibility lacked transparency and credibility for actors in rural areas, leading to fears of being left behind from the development in agglomeration areas.Die Umsetzung des Konzeptes der Metropolregionen in der planerischen Praxis war Hauptthema eines kürzlich an der Universität Tübingen abgeschlossenen Forschungsvorhabens. Zu den zentralen Fragen zählten Chancen, Hemmnisse und Herausforderungen bei der praktischen Umsetzung einer Politik, die auf Verbesserung der Wettbewerbsfähigkeit von Metropolregionen zielt. Bei der hier vorgestellten umfangreichen empirischen Studie liegt der Schwerpunkt auf dem Umsetzungsprozess in Baden-Württemberg. Dieses Bundesland bietet eine vielfältige Umsetzungslandschaft, die durch eine Vielzahl unterschiedlicher Ansätze geprägt ist. Dazu zählen sowohl die älteste als auch die jüngste Generation anerkannter Metropolregionen sowie grenzüberschreitende Einflussbereiche. Die Auswertung einer bei den Gemeindeverwaltungen durchgeführten Befragung - in Verbindung mit ausführlichen Interviews mit sonstigen Akteuren und Planungsbehörden - ermöglicht Einblick in einen dynamischen Prozess und weist auf signifikante Unterschiede sowohl bei der Planung als auch bei der Umsetzung hin. Erkennbar wird eine beträchtliche Lücke zwischen Theorie und Praxis, vor allem im Bereich der flexiblen Geometrien und bei den Strukturen der metropolitan governance. Die zunehmende Diskrepanz zwischen Funktions- und Verwaltungsräumen führt zu Tendenzen der Überdimensionierung und zu Marginalisierungsängsten. Bei dem vorgesehenen Konzept der großflächigen Verantwortungsgemeinschaften fehlte es für die Akteure in ländlichen Räumen an Transparenz und an Glaubwürdigkeit. Dazu zählte auch die Befürchtung der Abkopplung von der in den Agglomerationsräumen stattfindenden Entwicklung

Fabrication of bismuth-based photocatalytic heterojunctions for hydrogen generation

Das schnelle Bevölkerungswachstum und die Industrialisierung der letzten Jahrzehnte haben zu einer zunehmenden Umweltverschmutzung und einer hohen Nachfrage nach nicht erneuerbaren Energiequellen aus fossilen Brennstoffen geführt. Wasserstoff ist ein sauberer Energieträger, der aus der Dissoziation von Wasser und Sonnenenergie, einer erneuerbaren Quelle, gewonnen werden kann. Seit der Entdeckung der Wasserstoffentwicklung durch photoelektrochemische Wasserspaltung an n-Typ-TiO2-Elektroden wird die auf Halbleitern basierende photokatalytische Wasserspaltungstechnologie zur Erzeugung von Wasserstoff mit Hilfe von Sonnenenergie als einer der wichtigsten Ansätze zur Lösung der globalen Energiekrise angesehen. Die Entwicklung von Halbleiter-Photokatalysatoren ist daher in letzter Zeit Gegenstand erheblicher Forschungsanstrengungen gewesen. Die Synthese neuer, im sichtbaren Licht aktiver Photokatalysatoren mit hoher photokatalytischer Effizienz ist eine der größten Herausforderungen, bei der das Hauptproblem die schnelle Elektron-Loch-Rekombination ist. Das Design und die Herstellung von halbleitenden Heteroübergängen stellen eine Lösung für den Ladungsträgertransfer und die Trennung dar, um Reduktions- und Oxidationsreaktionen für die H2-Produktion zu erreichen. In der vorliegenden Arbeit wurden mit sichtbarem Licht betriebene Wismut-Heteroübergänge, die durch mechanisches Fräsen und thermisches Flammspritzen hergestellt wurden, für die photokatalytische Entwicklung von H2 in Gegenwart von Opferstoffen eingesetzt. Die Wirkung der Verarbeitungsparameter führte zu strukturellen Veränderungen, z.B. Gitterparameter, Kristallitgröße und Bindungsenergie, und damit zu Veränderungen ihrer optischen Eigenschaften, z.B. des Photolumineszenzsignals und der Bandlückenenergie, um die Oberflächenmodifikation und die Kopplung zwischen Halbleitern zu verstehen. Die Analyse der physikalisch-chemischen Eigenschaften dient dazu, den gewünschten Weg zur Synthese von Bi-basierten Heteroübergängen zu finden, die eine niedrige photogenerierte Elektron-Loch-Paar-Rekombination und eine hohe Absorption im sichtbaren Bereich des Sonnenspektrums nachahmen. In dieser Arbeit schlagen wir photokatalytische Reaktionsmechanismen für die H2-Evolution vor, die auf dem Bandkantenpotential jedes Halbleiters, der Bestimmung der photogenerierten Ladungsträger und der Erzeugung freier Radikale, gemessen durch paramagnetische Elektronenspektroskopie, basieren. Die Ergebnisse zeigen, dass der Aufbau eines Heteroübergangs in einer gestaffelten Technik wünschenswert ist, um den Ladungsträgertransfer und die Trennung zu verbessern. Die Stabilität des Halbleiters und einige physikochemische Eigenschaften wie Partikelgröße und Oberfläche dienen dazu, die Aktivität des Materials zu verbessern.Rapid population growth and industrialization in recent decades has led to increased environmental pollution and a high demand for non-renewable energy sources from fossil fuels. Hydrogen is a clean energy fuel that can be obtained from the dissociation of water and solar energy, a renewable source. Since the discovery of hydrogen evolution through photoelectrochemical water splitting on n-type TiO2 electrodes, semiconductor-based photocatalytic water splitting technology to produce hydrogen using solar energy has been considered as one of the most important approaches to solve the global energy crisis. Therefore, the development of semiconductor photocatalysts has recently been the subject of considerable research efforts. The synthesis of new visible-light active photocatalysts with high photocatalytic efficiencies is one of the main challenges in which the major problem is the fast electron-hole recombination. The design and fabrication of semiconducting heterojunctions represent a solution to address charge carrier transfer and separation to achieve reduction and oxidation reactions for H2 production. In the present work, visible light driven bismuth heterojunctions synthesized by mechanical milling and flame thermal spraying process were employed for the photocatalytic evolution of H2 in the presence of sacrificial agents. The effect of processing parameters induced structural modifications, for instance, lattice parameter, crystallite size, binding energy and thus led to changes in their optical properties, for instance, photoluminescence signal and band gap energy, to understand the surface modification and coupling between semiconductors. The analysis of physicochemical properties serves to achieve a desired route to synthesize Bi-based heterojunctions that lead to low photogenerated electron-hole pair recombination and high absorbance in the visible range of the solar spectrum. In this work, we propose photocatalytic reaction mechanisms for H2 evolution based on the band edge potential of each semiconductor, the determination of photogenerated charge carriers and free radical generation measured by electron paramagnetic spectroscopy. The results show that the construction of a heterojunction in a staggered engineering is desirable to improve charge carrier transfer and separation. The stability of the semiconductor and some physicochemical properties such as particle size and surface area serve to enhance the activity of the material

Investigating User Search Tactic Patterns and System Support in Using Digital Libraries

This study aims to investigate users\u27 search tactic application and system support in using digital libraries. A user study was conducted with sixty digital library users. The study was designed to answer three research questions: 1) How do users engage in a search process by applying different types of search tactics while conducting different search tasks?; 2) How does the system support users to apply different types of search tactics?; 3) How do users\u27 search tactic application and system support for different types of search tactics affect search outputs? Sixty student subjects were recruited from different disciplines in a state research university. Multiple methods were employed to collect data, including questionnaires, transaction logs and think-aloud protocols. Subjects were asked to conduct three different types of search tasks, namely, known-item search, specific information search and exploratory search, using Library of Congress Digital Libraries. To explore users\u27 search tactic patterns (RQ1), quantitative analysis was conducted, including descriptive statistics, kernel regression, transition analysis, and clustering analysis. Types of system support were explored by analyzing system features for search tactic application. In addition, users\u27 perceived system support, difficulty, and satisfaction with search tactic application were measured using post-search questionnaires (RQ2). Finally, the study examined the causal relationships between search process and search outputs (RQ 3) based on multiple regression and structural equation modeling. This study uncovers unique behavior of users\u27 search tactic application and corresponding system support in the context of digital libraries. First, search tactic selections, changes, and transitions were explored in different task situations - known-item search, specific information search, and exploratory search. Search tactic application patterns differed by task type. In known-item search tasks, users preferred to apply search query creation and following search result evaluation tactics, but less query reformulation or iterative tactic loops were observed. In specific information search tasks, iterative search result evaluation strategies were dominantly used. In exploratory tasks, browsing tactics were frequently selected as well as search result evaluation tactics. Second, this study identified different types of system support for search tactic application. System support, difficulty, and satisfaction were measure in terms of search tactic application focusing on search process. Users perceived relatively high system support for accessing and browsing tactics while less support for query reformulation and item evaluation tactics. Third, the effects of search tactic selections and system support on search outputs were examined based on multiple regression. In known-item searches, frequencies of query creation and accessing forwarding tactics would positively affect search efficiency. In specific information searches, time spent on applying search result evaluation tactics would have a positive impact on success rate. In exploratory searches, browsing tactics turned out to be positively associated with aspectual recall and satisfaction with search results. Based on the findings, the author discussed unique patterns of users\u27 search tactic application as well as system design implications in digital library environments